1. Field of the Invention
This invention relates to a condenser and an air conditioning refrigeration system using the condenser, and more particularly to, a condenser preferably used for an automobile air conditioning refrigeration system and an air conditioning refrigeration system using the condenser.
2. Description of Related Art
An automobile air conditioning refrigeration system is usually a vapor compressing system including a compressor, a condenser, an expansion valve and an evaporator.
A refrigerant state in such a refrigeration cycle is shown in FIG. 22 which shows a Mollier diagram having a vertical axis representing a pressure and a horizontal axis representing an enthalpy. In the diagram, the refrigerant is in a liquid phase in the left hand area of the liquid phase line, in a mixed phase including gas and liquid in the area between the liquid phase line and the vapor phase line, and in a vapor phase in the right hand area of the vapor phase line.
As shown in the solid line in FIG. 22, the refrigerant compressed by the compressor changes its status from the point A to the point B, resulting in a high-temperature and high-pressure gaseous refrigerant. Then, the gaseous refrigerant cooled by the condenser changes its status from the point B to the point C, resulting in a liquified refrigerant. Next, the liquified refrigerant is decompressed and expanded by the expansion valve to change its status from the point C to the point D, resulting in a low-pressure and low-temperature refrigerant in a mist or a gaseous state. Further, the refrigerant is evaporated by exchanging heat with ambient air in to the evaporator to change its status from the point D to the point A, resulting in a gaseous refrigerant. The enthalpy difference between the point D and the point A corresponds to a heat quantity for cooling ambient air. The larger the enthalpy difference is, the larger the refrigeration ability is.
Conventionally, in such a refrigeration cycle, a multi-flow type heat exchanger is well-known as a condenser for changing the refrigerant status from the point B to the point C. As shown in FIG. 23, the condenser is provided with a pair of headers 102 and a core 101. The core 101 is provided with a pair of headers 102 and a plurality of heat exchanging tubes disposed parallel to each other with the ends thereof communicated with the headers 102, 102. The plurality of heat exchanging tubes are divided into a plurality of passes P1, P2, P3 and P4 by partitions 103 provided in the headers 102. In the condenser, the refrigerant is condensed by exchanging heat with ambient air while flowing through each of the passes P1 to P4 in turn in a meandering manner.
As mentioned above, in the aforementioned refrigeration cycle, as mentioned above, the larger the enthalpy difference from the point D to the point A is, the larger the refrigeration ability is. In recent years, in the condensing process for changing the refrigerant status from the point B to the point C, a condenser which makes the enthalpy difference larger at the time of evaporation by sub-cooling the condensed refrigerant to the temperature several degrees lower than the point C to increase the heat rejection amount, has been developed.
An improved condenser having a receiver tank between the condensing zone and the sub-cooling zone has been proposed.
The condenser with the receiver tank, as shown in FIG. 24, is provided with a multi-flow type heat exchanger core 111 and a receiver tank 113 attached to one of the headers 112. An upstream portion of the heat exchanger core 111 constitutes a condensing zone 111C and a downstream portion of the heat exchanger core 111 constitutes a sub-cooling zone 111S. In this condenser, the refrigerant is condensed by exchanging heat with ambient air while flowing through each of the passes P1 to P3 of the condensing zone 111C in a meandered manner. Then, the condensed refrigerant is introduced into the receiver tank 113 to separate gaseous refrigerant and liquified refrigerant, and only the liquified refrigerant is introduced into the sub-cooling zone 111S to be sub-cooled.
In the refrigeration cycle using such a condenser, as shown in the dotted line in FIG. 22, the refrigerant compressed by the compressor changes its status from the point A to the point Bs, resulting in high-temperature and high-pressure gaseous refrigerant. Then, the gaseous refrigerant is cooled in the condensing zone 111C to change its status from the point Bs to the point Cs1, resulting in a liquified refrigerant. Furthermore, the liquified refrigerant flows through the receiver tank 113 and is sub-cooled in the sub-cooling zone 111S. Therefore, the refrigerant changes its status from the point Cs1 to the point Cs2, resulting in a perfect liquid refrigerant. Then, the liquid refrigerant is decompressed and expanded by the expansion valve and changes its status from the point Cs2 to the point Ds, resulting in a gaseous or mist refrigerant. Thereafter, the refrigerant is evaporated by the evaporator to change its status from the point Ds to the point A, resulting in a gaseous refrigerant.
In this refrigeration cycle, by sub-cooling the condensed refrigerant from the point Cs1 to the point Cs2 as shown in the diagram, the enthalpy difference (Ds to A) at the time of evaporation becomes larger than the enthalpy difference (D to A) at the time of evaporation in a normal refrigeration cycle. As a result, an excellent refrigeration effect can be obtained.
The conventional proposed condenser with a receiver tank is installed in a limited space in an engine room in the same manner as in the existing condenser shown in FIG. 23. Therefore, the size of the conventional proposed condenser with a receiver tank is basically the same as that of the existing condenser with no receiver tank. However, the lower portion of the conventional proposed condenser with a receiver tank constitutes a sub-cooling zone 111S which does not act so as to condensate the refrigerant. Therefore, the condensing zone 111C becomes smaller as compared to the existing condenser, resulting in a deteriorated condensing ability. Therefore, it is required to raise the refrigerant pressure by the compressor to send the higher-temperature and higher-pressure refrigerant to the condensing zone 111C so that the refrigerant can be assuredly condensed at such a low condensing ability. As a result, the refrigerant pressure in the refrigerant cycle, especially at the condensing zone in the refrigerant cycle, raises. As illustrated in the Mollier diagram shown in FIG. 22, in a refrigeration cycle using a conventional proposed condenser with a receiver tank, the refrigerant pressure at the condensing zone and the sub-cooling zone (Bs to Cs2) is higher than that of the normal refrigerant cycle.
As will be apparent from the above, in a conventional proposed condenser with a receiver tank, it is required to raise the refrigerant pressure, resulting in, for example, an increased load of a compressor, which in turn requires a large compressor and/or a high performance compressor. This causes a large and heavy system, resulting in a worse fuel consumption rate and an increased manufacturing cost.
An object of the present invention is to provide a condenser which can avoid an increase of refrigerant pressure and can obtain higher refrigeration effects.
The other object of the present invention is to provide an air conditioning refrigerant system with an enhanced performance without enlarging the size and weight.
According to one aspect of the present invention, a condenser includes a refrigerant inlet, a refrigerant outlet, a core portion having a refrigerant passage for introducing refrigerant from the refrigerant inlet to the refrigerant outlet while condensing the refrigerant, and decompressing means provided at a part of the refrigerant passage, the decompressing means decompressing a refrigerant pressure.
The condenser decompresses the refrigerant pressure when condensing the refrigerant. As shown in FIG. 4, the condenser constitutes, for an example, an automobile air conditioning refrigeration system together with a compressor 2, an evaporator 4, an expansion valve 3, a receiver tank 5 and so on.
In the refrigeration system using the condenser according to the present invention, as shown in an solid line of the Mollier diagram shown in FIG. 5, the refrigerant is compressed by the compressor 2 to change the status from the point A to the point B to become a high-temperature and high-pressure gaseous refrigerant. Then, the gaseous refrigerant is condensed in the refrigerant passage located between the refrigerant inlet and the decompressing means to change the status from the point B to the point Ct1 to become a liquified refrigerant. Thereafter, the liquified refrigerant is decompressed to change its status from the point Ct1 to the point Ct2 to become a low-temperature and a low-pressure gaseous refrigerant. Then, the gaseous refrigerant is re-condensed in the refrigeration passage between the decompressing means and the refrigeration outlet to change its status from the point Ct2 to the point Ct3. Thus re-condensed refrigerant flows out of the refrigerant outlet and is introduced into a receiver tank 5. In the receiver tank 5, the refrigerant is separated into a liquified refrigerant and a gaseous refrigerant. Thereafter, only the liquified refrigerant is decompressed and expanded by the expansion valve 3 to change its status from the point Ct3 to the point Dt to become a low-pressure and a low-temperature gaseous or mist refrigerant. Then, the decompressed and expanded gaseous refrigerant is exchanged heat with ambient air by the evaporator 4 to be evaporated to change the status from the point Dt to the point A, resulting in a gaseous refrigerant.
As will be understood from the above explanation, the condenser of the present invention conducts a first condensing (B to Ct1), a decompressing (Ct1 to Ct2) and a second condensing (Ct2 to Ct3) in the aforementioned refrigeration cycle.
In the condenser, the refrigerant increases heat absorption ability by the loss of heat in the first condensing. Thereafter, the refrigerant further increases heat absorption ability by being decompressed and re-condensed. As a result, the difference of the enthalpy can be made larger at the time of evaporation, resulting in an excellent refrigeration effect. For example, the refrigeration cycle using the condenser of the present invention can obtain the same difference of the enthalpy (Dt to A) at the time of the evaporation as in the conventional proposed refrigeration cycle using a condenser with a receiver tank (see dotted line in FIG. 5), resulting in an excellent refrigeration effect.
Furthermore, the condenser according to the present invention releases heat from the refrigerant by the first and second condensations in which the phase of the refrigerant is changed, which enables an efficient release of heat as compared to the conventional proposed condenser with a receiver tank in which the heat is released by a sub-cooling without casing the phase change. In other words, the condenser according to the present invention utilizes almost all of the area as a condensing zone, which enables an efficient heat releasing, resulting in an enhanced condensing ability. Therefore, the refrigerant can be assuredly condensed without raising the refrigerant pressure in the refrigeration cycle, which in turn can decrease the load of compressor. Therefore, it is not necessary to use a large compressor, and is possible to make the refrigeration system small in size and light in weight and to enhance the fuel consumption rate at the time when the condenser is mounted in an automobile.
In the present invention, it is not necessary to completely evaporate the refrigerant by the decompressing means, and it is allowed to introduce the liquified refrigerant condensed at the upstream side of the decompressing means to the downstream side of the decompressing means without evaporating the refrigerant as it is.
However, in order to effectively prevent the refrigerant pressure rise, it is preferable to evaporate at least a part of the liquified refrigerant by the decompressing means and then to re-condense (secondly condense) the refrigerant.
It is preferable that the refrigerant passage located at an upstream side of the decompressing means condensates at least a part of high-pressure gaseous refrigerant into a liquified refrigerant, wherein the decompressing means decompresses the liquified refrigerant into a low-pressure gaseous refrigerant, and wherein the refrigerant passage located at a downstream side of the decompressing means re-condensates the low-pressure gaseous refrigerant.
It is preferable that the refrigerant passage located at an upstream side of the decompressing means condensates at least a part of high-pressure gaseous refrigerant into a liquified refrigerant, wherein the decompressing means decompresses the liquified refrigerant into a low-pressure gaseous refrigerant, and wherein the refrigerant passage located at a downstream side of the decompressing means re-condensates the low-pressure gaseous refrigerant.
Furthermore, it is preferable that a liquid holding portion for holding the liquified refrigerant is provided at the upstream side of the decompressing means.
The refrigerant passage cross-sectional area of the decompressing means may be smaller than a cross-sectional area of the refrigerant passage located at an upstream side of the decompressing means and that of the refrigerant passage located at a downstream side of the decompressing means.
It is preferable that the core portion includes a plurality of heat exchanging tubes with opposite ends thereof connected to a pair of spaced parallel headers in fluid communication. In this case, it is preferable that at least one partition provided in at least one of the headers to divide the plurality of heat exchanging tubes into a plurality of passes is further provided, whereby the refrigerant passes each of the passes in turn, wherein the plurality of passes include a first pass to which the refrigerant inlet is connected and a final pass to which the refrigerant outlet is connected, and wherein the decompressing means is disposed at a part of the refrigerant passage located between the first pass and the final pass.
The plurality of passes may include the first pass, the final pass and one or a plurality of intermediate passes, and wherein at least one of the intermediate passes constitutes a decompressing pass as the decompressing means.
The decompressing means may be provided in the header.
The decompressing means may include a plate member partitioning an inside of the header and an orifice tube penetrating the plate member for passing refrigerant.
Alternatively, the decompressing means may be a reduced diameter portion of the header.
Furthermore, the decompressing means may include a plate member partitioning an inside of the header and a refrigerant detour pipe with one end thereof connected to the header in fluid communication at an upstream side of the plate member and the other end thereof connected to the header in fluid communication at a downstream side of the plate member.
In a case of a multi-flow type condenser, it may comprise a receiver tank, wherein the receiver tank is disposed at an upstream side of the decompressing means so that the receiver tank receives liquified refrigerant liquified by the refrigerant passage located at an upstream side of the decompressing means to separate the liquified refrigerant into a liquid refrigerant and a gaseous refrigerant and introduces the liquid refrigerant into the decompressing means, whereby the liquid refrigerant is decompressed by the decompressing means into a low-pressure gaseous refrigerant which in turn is re-condensed by the refrigerant passage located at a downstream side of the decompressing means.
According to the second aspect of the present invention, a refrigeration system for use in an air conditioner which constitutes a refrigeration cycle in which refrigerant is sealed, comprising:
a compressor;
a condenser;
a decompressing member such as an expansion valve; and
an evaporator,
wherein the condenser includes:
a refrigerant inlet for introducing refrigerant sent from the compressor into the condenser;
a refrigerant outlet for sending the refrigerant from the condenser to the decompressing member;
a heat exchanging portion having a refrigerant passage for introducing the refrigerant to the refrigerant outlet while condensing the refrigerant introduced from the refrigerant inlet; and
a decompressing portion provided at a part of the refrigerant passage for decompressing a refrigerant pressure,
wherein the heat exchanging portion includes a pair of parallel headers disposed at a certain distance, a plurality of heat exchanging tubes with opposite ends connected to the headers in fluid communication and at least one partitioning member provided at at least one of the headers to divide the plurality of heat exchanging tubes into a plurality of heat exchanging passes, whereby the refrigerant passes through each of the passes in turn,
wherein the plurality of passes include a first pass connected to the refrigerant inlet and a final pass connected to the refrigerant outlet,
wherein the decompressing portion is provided at a part of the refrigerant passage between the first pass and the final pass,
wherein the decompressing portion has a passage cross-sectional area smaller than a cross-sectional area of the refrigerant passage adjacent to the decompressing portion at an upstream side of the decompressing portion and that of the refrigerant passage adjacent to the decompressing portion at a downstream side of the decompressing portion,
wherein the refrigerant passage located at an upstream side of the decompressing means condenses at least a part of a high-pressure gaseous refrigerant compressed by the compressor by exchanging heat between the high-pressure gaseous refrigerant and ambient air into a liquified refrigerant,
wherein the decompressing portion decompresses the liquified refrigerant into a low-pressure gaseous refrigerant, and
wherein the refrigerant passage located at a downstream side of the decompressing means re-condenses the low-pressure gaseous refrigerant by exchanging heat between the low-pressure gaseous refrigerant and ambient air.